ETL error - "Row cannot be located ..."

Please consider this as a severity.
We encounter this error in our production (live). ETL version we use is 5.8.0.6

It is been a while since I have seen this error message

There are a lot of information in the internet about it

www.google.com/search?q=row+cannot+be+lo...Ly8gegJ&ved=0CBEQvwU

It might happend if 2 different users try to update same record at the same time.

We will of course try to reproduce the problem here

Just to let you know. I ran this ETL package manually and no other instances of the same package or user.
This appeared twice today after several runs of this package (every 2 mins).
Our database is SQL Server 2008 R2.

Since you mentioned "might happened if 2 different users try to update.." - is this kind of error related to a "application" logic of the package or the ETL way of accessing the database?
As you can see from the screen shot, this error occurred during copying of tif file/s from one place to another. (loop thru image node to copy tif image node).

Please explain any possible scenarios that ETL might get this kind of error.

we are thinking of indexing our ETL Repository database. Please advise.

"We are thinking of indexing our ETL Repository database. Please advise."

This might be related, all indexes are created for you when you run repository creation scripts.

We are in process of restoring source for version 5.8.0.6 from SVN.
It is very time consuming operation.

Once we are able to build version 5.8.0.6 we will run series of tests in order to try to reproduce the problem

I provided you our ETL repository database (ETLRepositoryDB) before - that one still in version 5.8.0.6. You can use that for testing if you want to.